The present invention relates to a method of feeding collars to a continuous packing line for producing rigid packets of cigarettes.
Machines for packing cigarettes in rigid packets are known to feature continuous packing lines comprising a pocket conveyor for continuously and successively feeding groups of cigarettesxe2x80x94wrapped in respective protective wrappings preferably of foilxe2x80x94through a collar supply station.
The collars are normally fed to the supply station by a supply unit comprising a feed assembly for feeding the collars in steps to a pickup station in a direction perpendicular to a major dimension of the collars. The supply unit also comprises a transfer wheel rotating continuously about a respective axis, and from the periphery of which extend outwards a number of transfer arms, each for transferring a respective collar from the pickup station to the supply station. When transferring the respective collar, each transfer arm moves through a folding station where the lateral wings of the collar are folded squarely with respect to a central panel of the collar. Each transfer arm is then rotated 90xc2x0 about a respective longitudinal axis to feed the respective collar through the supply station in a direction parallel to said major dimension of the collar, and on to the respective group of cigarettes, which is fed through the supply station in a direction crosswise to a respective longitudinal axis.
Each known transfer arm normally comprises a base fitted to the periphery of the transfer wheel to rotate, with respect to the transfer wheel, about a respective axis parallel to the axis of the transfer wheel; a shaft fitted to the base to rotate, with respect to the base, about a respective longitudinal axis extending outwards from the transfer wheel in a substantially radial direction; and a pickup member for engaging a respective collar, and which is connected to a free end of the shaft to rotate, with respect to the shaft, about a respective axis parallel to the axis of the transfer wheel.
The collar feed assembly comprises a feed device for feeding a strip of cardboard in steps to a cutting station coinciding with the pickup station; and a cutting device for cutting the collars successively off the strip, and which normally comprises an anvil having a face coplanar with the strip, and a knife movable to and from the anvil to cut off the collars.
The complex articulated structure of the transfer arm is necessary to enable the respective pickup member to substantially stop at the pickup station long enough to safely pick up a respective collar, to cooperate with the continuous packing conveyor to transfer the collar to a respective pocket, and to rotate 90xc2x0 about its own longitudinal axis between the folding station and the transfer station. In particular, when picking up the collar at the cutting station, the pickup member must be maintained for a given length of time substantially facing and contacting the collar to ensure precise, reliable pickup.
A collar supply unit of the type described above has several major drawbacks, both technical and economic, on account of the complex structure of each transfer arm.
It is an object of the present invention to provide a straightforward, low-cost method of transferring collars from a step-operated feed device to a continuous conveyor.
According to the present invention, there is provided a method of feeding collars to a continuous packing line for producing rigid packets of cigarettes, the method comprising a feed step to feed a strip in steps to a cutting station; a cutting step to cut said strip and obtain from the strip a succession of collars; and a transfer step to transfer the collars continuously to a packing wheel; and being characterized in that, during said cutting step, a cutting knife and a pickup member for picking up a said collar are swung in time with each other substantially about a same first axis and with concordant, substantially identical laws of motion, so that, at said cutting station, said cutting knife and said pickup member are maintained substantially contacting each other with, in-between, a said collar just cut off said strip.
According to a preferred embodiment of the above method, said pickup member comprises a pickup surface which is brought into contact with said collar; said pickup surface being perpendicular to a second axis, which is crosswise to said first axis and is maintained, during said cutting step, in a position substantially intersecting said first axis.